Vehicle suspension system with multi-stage hydraulic cylinder assemblies and external spring packs

ABSTRACT

A vehicle suspension connects a vehicle body to a plurality of wheels and allows relative motion between the vehicle body and the wheels. The suspension system includes a plurality of telescoping multi-stage hydraulic cylinder assemblies arranged to selectively lift the vehicle body relative to the wheels when extended and to lower the vehicle body relative to the wheels when contracted. A control valve is used to adjust a volume of hydraulic fluid in the hydraulic cylinder assemblies to change a height of the vehicle. External spring packs are in fluid connection with the hydraulic cylinder assemblies to maintain spring forces on the suspension system over a range of telescopic movement of the hydraulic cylinder assemblies. Fluid damping valves are provided for damping telescopic movement of the hydraulic cylinder assemblies by restricting fluid flow between the hydraulic cylinder assemblies and the spring packs.

RELATED APPLICATIONS

This application is related to Applicant's U.S. patent application Ser.No. 15/607,482 filed on May 27, 2017, which was issued as U.S. Pat. No.10,214,071 on Feb. 26, 2019, and Applicant's U.S. Provisional PatentApplication No. 62/342,926 filed on May 28, 2016. The entire contents ofthese related applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to vehicle suspension systems, and inparticular to a vehicle suspension system having vehicle heightadjustment.

Description of the Prior Art

Height adjustment devices for vehicle suspensions are known in the priorart. For example, U.S. Patent Application Publication No. 2016/0229253of Seminara discloses a suspension strut for a motor vehicle with aheight-adjustment device. Such devices have been used with MacPhersonsuspensions on sport utility vehicles to position the vehicle body at agreater height from the ground when the vehicle is running off road, andat a smaller height from the ground when the vehicle is running on road.Such devices have also been used on sports cars, for example, to reducethe vehicle height to ensure better driving conditions at high speed.

In a typical vehicle suspension system, single stage shock absorbers areused that have a single piston/shaft sliding in a single cylindricaltube. Such shock absorbers have an extended length less than twice acompressed length. Single stage shock absorber are widely used forordinary vehicle suspension systems.

Multi-stage hydraulic cylinder assemblies for vehicle suspensions havealso been described in the prior art. For example, U.S. PatentApplication Publication No. 2014/0291085 of Bandy discloses a segmentedair shock absorber that uses an oil-gas emulsion air shock design withshock damping and suspension spring properties. For another example,U.S. Pat. No. 8,967,346 of Polakowski et al. discloses a multi-stagetelescopic shock absorber that contains an internal damping chamber fordamping shock forces applied to the shock absorber. For another example,U.S. Pat. No. 3,363,894 of Hill discloses a dual spring rate shock strutfor use as an aircraft strut to provide a substantially constant strutextension over a range of static loads of the aircraft.

However, none of the multi-stage cylinder assemblies described aboveprovide a system that can be used to provide vehicle height adjustmentover a wide range for variable ride height while maintaining aconsistent and acceptable ride quality.

There is a need in the industry for an improved vehicle suspensionsystem that allows a wide range of vehicle height adjustments whilemaintaining a compact multi-stage configuration that also providesconsistent spring forces and desired ride quality.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a vehicle suspensionsystem having multi-stage hydraulic cylinder assemblies that provideheight adjustment in a range greater than a length of the hydrauliccylinder assemblies in their fully contracted condition.

A further object of the present invention is to provide a vehiclesuspension system having multi-stage hydraulic cylinder assemblies influid communication with external spring packs and damping valves toprovide consistent spring forces and ride quality over a wide range ofvehicle height adjustments.

A further object of the present invention is to provide a vehiclesuspension system having a multi-stage hydraulic cylinder assemblyassociated with each of the wheels of the vehicle.

A further object of the present invention is to provide a vehiclesuspension system having an anti-sway system that uses a plurality ofmulti-stage hydraulic cylinder assemblies and fluid lines connectedtherebetween.

To accomplish these and other objects, the present invention provides avehicle suspension that connects a vehicle body to a plurality of wheelsand allows relative motion between the vehicle body and the wheels. Thesuspension system includes a plurality of telescoping multi-stagehydraulic cylinder assemblies arranged to selectively lift the vehiclebody relative to the wheels when extended and to lower the vehicle bodyrelative to the wheels when contracted. A control valve is used toadjust a volume of hydraulic fluid in the hydraulic cylinder assembliesto change a height of the vehicle. External spring packs are in fluidconnection with the hydraulic cylinder assemblies to maintain springforces on the suspension system over a range of telescopic movement ofthe hydraulic cylinder assemblies. Fluid damping valves are provided fordamping telescopic movement of the hydraulic cylinder assemblies byrestricting fluid flow between the hydraulic cylinder assemblies and thespring packs.

According to one aspect of the present invention, a vehicle suspensionsystem is provided comprising: a telescoping multi-stage hydrauliccylinder assembly arranged to selectively lift a vehicle body relativeto a vehicle wheel when extended and lower the vehicle body relative tothe vehicle wheel when contracted; an external spring pack in fluidconnection with the hydraulic cylinder assembly to maintain a springforce on the suspension system over a range of telescopic movement ofthe hydraulic cylinder assembly; and a fluid damping valve for dampingtelescopic movement of the hydraulic cylinder assembly by restrictingfluid flow between the hydraulic cylinder assembly and the spring pack.

According to another aspect of the present invention, a vehicle isprovided comprising: a vehicle body; a plurality of wheels; and asuspension system that connects the vehicle body to the plurality ofwheels and allows relative motion between the vehicle body and thewheels. The suspension system comprises: a plurality of telescopingmulti-stage hydraulic cylinder assemblies arranged to selectively liftthe vehicle body relative to the wheels when extended and to lower thevehicle body relative to the wheels when contracted; a plurality ofexternal spring packs in fluid connection with the plurality ofhydraulic cylinder assemblies to maintain spring forces on thesuspension system over a range of telescopic movement of the hydrauliccylinder assemblies; and a plurality of fluid damping valves for dampingtelescopic movement of the hydraulic cylinder assemblies by restrictingfluid flow between the hydraulic cylinder assemblies and the springpacks.

According to another aspect of the present invention, a vehiclesuspension is provided comprising: first and second telescopingmulti-stage hydraulic cylinder assemblies mounted on right and leftsides of a vehicle, respectively, the hydraulic cylinder assembliesbeing arranged to selectively lift the vehicle when extended and lowerthe vehicle when contracted, wherein each of the hydraulic cylinderassemblies comprises a plurality of cylinders nested within each other,wherein a length of each of the hydraulic cylinder assemblies in a fullyextended condition is more than a length thereof in a fully contractedcondition, and wherein each of the hydraulic cylinder assemblies aretwo-way cylinder assemblies having a pressure side and a reservoir side;first and second external spring packs in fluid connection with thefirst and second hydraulic cylinder assemblies, respectively, tomaintain spring forces on the hydraulic cylinder assemblies over a rangeof telescopic movement of the hydraulic cylinder assemblies; fluiddamping valves for damping movement of the hydraulic cylinder assembliesby restricting fluid flow between the hydraulic cylinder assemblies andthe spring packs; and an anti-sway system comprising a first anti-swayfluid line connected between a pressure side of the first hydrauliccylinder assembly and a reservoir side of the second hydraulic cylinderassembly, and a second anti-sway fluid line connected between a pressureside of the second hydraulic cylinder assembly and a reservoir side ofthe first hydraulic cylinder assembly.

Numerous other objects of the present invention will be apparent tothose skilled in this art from the following description wherein thereis shown and described embodiments of the present invention, simply byway of illustration of some of the modes best suited to carry out theinvention. As will be realized, the invention is capable of otherdifferent embodiments, and its several details are capable ofmodification in various obvious aspects without departing from theinvention. Accordingly, the drawings and description should be regardedas illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more clearly appreciated as thedisclosure of the invention is made with reference to the accompanyingdrawings. In the drawings:

FIG. 1 is a diagram illustrating a vehicle suspension system havingtelescoping multi-stage hydraulic cylinder assemblies and externalspring packs according to the present invention.

FIG. 2 is an elevation view showing a telescoping multi-stage hydrauliccylinder assembly of the present invention installed in a vehicle inplace of a conventional rear shock absorber.

FIG. 3 is an elevation view showing a telescoping multi-stage hydrauliccylinder assembly of the present invention installed in a vehicle inplace of a conventional front shock absorber.

FIG. 4 is a perspective view of a telescoping multi-stage hydrauliccylinder assembly used in the vehicle suspension system of the presentinvention.

FIG. 5 is a cross section view of the telescoping multi-stage hydrauliccylinder assembly in a contracted position.

FIG. 6 is a cross section view of the telescoping multi-stage hydrauliccylinder assembly in an extended position.

FIG. 7 is a plan view of an external spring pack used in the vehiclesuspension system of the present invention.

FIG. 8 is a cross section view of the external spring pack shown in FIG.7.

FIG. 9 is a cross section diagram of an external spring pack that uses acoil spring to apply a spring force to the hydraulic fluid in thevehicle suspension system.

FIG. 10 is a cross section diagram of an external spring pack that usesa coil spring and a pressurized gas to apply a spring force to thehydraulic fluid in the vehicle suspension system.

FIG. 11 is a cross section diagram of an external spring pack that usesa pressurized gas to apply a spring force to the hydraulic fluid in thevehicle suspension system.

FIG. 12 is a diagram illustrating a vehicle suspension system having asway control system according to the present invention.

FIG. 13 is a plan view of a spare tire compartment under a pickup truckbed with a hydraulic reservoir of the vehicle suspension system of thepresent invention nested in a spare tire for the vehicle.

DETAILED DESCRIPTION OF THE INVENTION

A vehicle suspension system 10 according to the present invention willnow be described in detail with reference to FIGS. 1 to 13 of theaccompanying drawings.

The vehicle suspension system 10 of the present invention can replaceconventional shock absorbers found in a vehicle V. The vehiclesuspension system 10 can also replace traditional spring components andanti-sway systems used on many vehicles.

As illustrated in FIG. 1, the vehicle suspension system 10 includestelescoping multi-stage hydraulic cylinder assemblies 11, 12. Thehydraulic cylinder assemblies 11, 12 are shown in a fully extendedposition in FIG. 1. The hydraulic cylinder assemblies can be one-wayhydraulic cylinder assemblies 11, 12, as shown in FIG. 1, or two-wayhydraulic cylinder assemblies 11′, 12′, as shown in FIG. 12. Thehydraulic cylinder assemblies 11, 12 are each arranged to selectivelylift the vehicle body 13 relative to a vehicle wheel 14, 15 whenextended, and to lower the vehicle body 13 relative to the vehicle wheel14, 15 when contracted.

As illustrated in FIGS. 2 and 3, the hydraulic cylinder assemblies 11,12 can be installed on the vehicle V in place of conventional shockabsorbers. For example, the hydraulic cylinder assemblies 11, 12 can beinstalled to existing upper and lower shock absorber mounting pins/boltsB adjacent to a rear wheel 14 of the vehicle V (FIG. 2) or a front wheel15 of the vehicle V (FIG. 3). The conventional leaf springs (not shown)and coil springs (not shown) for the vehicle V can also be removedbecause their functions are provided by the hydraulic cylinderassemblies 11, 12 and other components of the vehicle suspension system10 of the present invention.

The hydraulic cylinder assemblies 11, 12 illustrated in the drawings ofthis application are two-stage cylinder assemblies having a basecylinder 16, an intermediate cylinder 17 arranged for sliding movementwithin the base cylinder 16, and a shaft 18 arranged for slidingmovement within the intermediate cylinder 17. As illustrated in FIG. 6,the base cylinder 16 and the intermediate cylinder 17 together define asingle internal chamber. As illustrated in FIG. 5, seals 19 are providedbetween the base cylinder and the intermediate cylinder, and seals 20are provided between the intermediate cylinder 17 and the shaft 18. Afirst coupler 21 is provided on the upper end of the base cylinder 16for attaching to an upper shock absorber mounting bolt B. A secondcoupler 22 is provided on the lower end of the shaft 18 for attaching toa lower shock absorber mounting bolt B.

In a contracted condition of the hydraulic cylinder assemblies 11, 12(as shown in FIG. 5), the intermediate cylinder 17 telescopes or nestswithin the base cylinder 16, and the shaft 18 telescopes or nests withinthe intermediate cylinder 17. In an extended condition of the hydrauliccylinder assemblies 11, 12 (as shown in FIGS. 1, 4 and 6), theintermediate cylinder 17 protrudes out of the base cylinder 16, and theshaft 18 protrudes out of the intermediate cylinder 17. A length of thehydraulic cylinder assemblies 11, 12 in a fully extended condition ismore than double a length of the hydraulic cylinder assemblies 11, 12 ina fully contracted condition.

Additional stages can be added to the hydraulic cylinder assemblies 11,12 to increase a length of the hydraulic cylinder assemblies 11, 12 whenfully extended. For example, instead of a two-stage cylinder assemblyhaving one intermediate cylinder 17, a three-stage cylinder assemblyhaving two intermediate cylinders can be used to increase an extendedlength of the cylinder assembly.

By using multi-stage hydraulic cylinder assemblies 11, 12, it ispossible to have a shock absorber-like member that can extend numeroustimes its compressed height. This allows a long extension range in alimited space envelope, which can be particularly useful in a suspensionsystem that requires a wide range of travel. For example, a two-stagehydraulic cylinder assembly 11, 12 can extend approximately two timesthe compressed height, while a four-stage hydraulic cylinder assemblycan extend approximately four times the compressed height. In contrast,a traditional shock absorber used in most vehicle suspensions uses asingle-stage assembly having approximately a 1:1 ratio or less of anextension.

The vehicle suspension system 10 includes external spring packs 23, 24in fluid connection with the single internal chambers of the hydrauliccylinder assemblies 11, 12. The external spring packs 23, 24 function tomaintain a spring force on the suspension system over a range oftelescopic movement of the hydraulic cylinder assemblies 11, 12. Thespring packs 23, 24 are located remote from the hydraulic cylinderassemblies 11, 12. For example, the spring packs 23, 24 can be mountedat a central location on the vehicle V and connected to the hydrauliccylinder assemblies 11, 12 by hydraulic lines 25, 26.

The spring packs 23, 24 can have a variety of different forms. Forexample, as illustrated in FIGS. 7 and 8, the spring packs 23, 24 canhave a cylindrical chamber 27 having a port 28 at one end for connectinga hydraulic line in fluid connection with the hydraulic cylinderassembly 11, 12. A piston plunger 29 having a seal 30 that engages aninner cylindrical surface 31 of the chamber 27 is arranged for slidingmovement within the cylindrical chamber 27. A coil spring 32 is arrangedon a spring side 33 of the chamber 27 to bias the piston plunger 29 in adirection that applies positive hydraulic pressure on a fluid side 34 ofthe chamber 27 to the hydraulic cylinder assembly 11, 12. A second port35 in the other end of the cylindrical chamber 27 can be used to ventthe spring side 33 of the chamber 27 during movement of the pistonplunger within the chamber 27, or to provide a secondary source ofspring force (e.g., pneumatic pressure) to the piston plunger 29. Thespring packs 23, 24 can be constructed with a removable end 36 to allowfor relatively easy spring removal or replacement/variation.

FIGS. 9 to 11 illustrate various configurations and springs that can beused for the external spring packs 23, 24. Specifically, FIG. 9 shows aspring pack 23, 24 having a coil spring 32 used to apply a mechanicalspring force to the piston plunger 29 in the spring pack 23, 24; FIG. 10shows a spring pack 23′ having a coil spring 32 and a pressurized gasused to apply a combined mechanical and compressed gas spring force tothe piston plunger 29; and FIG. 11 shows a spring pack 23″ having acompressed gas chamber used to apply a compressed gas spring force tothe piston plunger 29. In each of these variations, a spring force isimparted to the piston plunger 29 in the spring pack 23, 23′, 23″, whichin turn causes a hydraulic pressure to be applied to the fluid in theassociated hydraulic cylinder assembly 11, 12.

The external spring packs 23, 24 maintain a substantially constantspring force on the suspension system 10 over a range of telescopicmovement of the hydraulic cylinder assemblies 11, 12 to accommodateheight changes of the vehicle V while maintaining a comfortable ride.The spring rate of the external spring packs 23, 24 will remainsubstantially constant during a full range of movement of the hydrauliccylinder assemblies 11, 12.

However, the effective spring rate will vary for each stage of extensionof the hydraulic cylinder assemblies 11, 12. For example, when thehydraulic cylinder assemblies 11, 12 are contracted to their first stage(i.e., the intermediate cylinder 17 is extended less than its fulllength from the base cylinder 16), the effective cross section of thehydraulic cylinder assembly 11, 12 is relatively large based on theinternal diameter of the base cylinder 16. This will cause a stifferride for the vehicle because each increment of movement of the hydrauliccylinder assembly 11, 12 will result in a relatively greater movement ofthe spring 32 in the external spring pack 23, 24.

When the hydraulic cylinder assemblies 11, 12 are extended to theirsecond stage, the effective cross section of the hydraulic cylinderassembly 11, 12 is relatively smaller based on the internal diameter ofthe intermediate cylinder 17. This will cause a softer ride for thevehicle because each increment of movement of the hydraulic cylinderassembly 11, 12 will result in a relatively smaller movement of thespring 32 in the external spring pack 23, 24. Thus, the multi-stageaspect of the hydraulic cylinder assemblies 11, 12 provides an automaticchange in the effective spring rate of the vehicle based on the adjustedheight of the suspension (i.e., stiffer ride when the height is adjustedto a low setting, and softer ride when the height is adjusted to a highsetting).

The vehicle suspension system 10 includes fluid damping valves 37, 38that restrict hydraulic fluid flow between the hydraulic cylinderassemblies 11, 12 and the external spring packs 23, 24. The fluiddamping valves 37, 38 function to dampen telescopic movement of thehydraulic cylinder assemblies 11,12 during operation of the vehicle overvarying terrain and operating conditions. The fluid damping valves 37,38 are inline systems that dampen fluid forces as hydraulic fluid passesin either direction between the hydraulic cylinder assemblies 11, 12 andthe external spring packs 23, 24.

A controller 39 is provided to control a control valve assembly 40 forregulating flow of hydraulic fluid into and out of the suspension system10. The control valve assembly 40 has a plurality of control valves withsolenoids in a ported block. The control valves each have a pressureinlet port connected to a hydraulic pump that provides a pressure source41 for the system 10, and a return port connected to a hydraulicreservoir 42. The hydraulic pump 41 can be, for example, a 12 volthydraulic pump mounted inside of a frame rail of the vehicle. The pump41 is connected by hydraulic lines to pull fluid from the reservoir 42and to supply fluid pressure to the control valve assembly 40.

The control valves in the control valve assembly 40 each have a firstposition in which hydraulic fluid flows from the pressure inlet to arespective one of the hydraulic cylinder assemblies 11, 12, a secondposition in which hydraulic fluid flows through from a respective one ofthe hydraulic cylinder assemblies 11, 12 to the hydraulic reservoir 42,and a third position in which hydraulic fluid is blocked from flowingthrough the control valve. The control valves are moved between theirpositions to individually control a flow of hydraulic fluid from thepressure source 41 to each of the hydraulic cylinder assemblies 11, 12,and a flow of hydraulic fluid out of each of the hydraulic cylinderassemblies 11, 12 to the reservoir 42.

The volume of hydraulic fluid maintained in the hydraulic cylinderassemblies 11, 12 determines the extended length of the hydrauliccylinder assemblies 11, 12, and hence, the height of the vehicle body 13relative to the vehicle wheels 14, 15. The control valve assembly 40 canprovide independent controls for the hydraulic cylinder assemblies 11,12 independent of each other, or in multiples.

Suspension position sensors 43 are arranged on the vehicle V to measurea position of the vehicle body 13 relative to a respective vehicle wheel14, 15 to provide feedback for adjusting a height and levelness of thevehicle body 13. Outputs signals from the position sensors 43 arecommunicated to the controller 39 for use in the height and levelcontrol.

A user interface 44 is provided to allow a user to change a height ofthe vehicle body 13. The user interface 44 may include, for example, acell phone app utilizing a WiFi module connected to the controller 39, ahardwired remote input device on the vehicle, or an integrated Bluetoothconnection through an on-board vehicle interface/navigation panel.Through any of these input devices, the operator can move any corner ofthe vehicle up or down independently or collectively by changing avolume of hydraulic fluid in the hydraulic cylinder assemblies 11, 12.

The user can set multiple preset heights that the controller willmaintain automatically through a key-on cycle or drive cycle. Forexample, the controller 39 can be programmed to cause the vehicle to goto an operator pre-chosen ride height setting upon establishing theoperator's identity through a pre-programmed key setting. For a secondexample, the operator can select a low vehicle height setting tofacilitate exiting the vehicle or driving in a low ceiling area, and thecontroller 39 will cause the control valve assembly 40 to adjust theheight of the hydraulic cylinder assemblies 11, 12 accordingly. For athird example, when an operator hooks onto a heavy trailer changing thevehicle rake, the controller 39 can auto level the vehicle to accountfor the additional loads. The controller 39 can also adjust lean angleson cornering or side hills based on inputs from accelerometer typesensors contained in the controller 39 or elsewhere on the vehicle.

The vehicle suspension 50 according to the present invention can also beused to provide an anti-sway feature for the vehicle, thus eliminating aneed for other anti-sway components on the vehicle, such as anti-swaybars and links. As illustrated in FIG. 12, the suspension system 50includes a pair of telescoping multi-stage hydraulic cylinder assemblies11′, 12′ mounted on right and left sides of the vehicle, respectively.The hydraulic cylinder assemblies 11′, 12′ are arranged to selectivelylift the vehicle when extended and lower the vehicle when contracted. Asin the embodiments described above, each of the hydraulic cylinderassemblies 11′, 12′ has a plurality of cylinders telescoped or nestedwithin each other, and a length of each hydraulic cylinder assembly 11′,12′ in a fully extended condition is more than double a length thereofin a fully contracted condition.

The hydraulic cylinder assemblies 11′, 12′ in this embodiment aretwo-way cylinder assemblies having a primary side 51, 53 and a secondaryside 52, 54. The primary sides 51, 53 of the cylinder assemblies 11′,12′ are connected by hydraulic lines 55, 56 to respective fluid dampingvalves 57, 58 and external spring packs 59, 60. As in the embodimentsdescribed above, the external spring packs 59, 60 function to maintainspring forces on the hydraulic cylinder assemblies 11′, 12′ over a rangeof telescopic movement of the hydraulic cylinder assemblies 11′, 12′,and the damping valves 57, 58 function to restrict fluid flow betweenthe hydraulic cylinder assemblies 11′, 12′ and the spring packs 59, 60to dampen the movement of the hydraulic cylinder assemblies 11′, 12′.

An anti-sway system is provided by having a first anti-sway fluid line61 connected between the primary side 51 of the first hydraulic cylinderassembly 11′ and the secondary side 54 of the second hydraulic cylinderassembly 12′, and a second anti-sway fluid line 62 connected between theprimary side 53 of the second hydraulic cylinder assembly 12′ and thesecondary side 52 of the first hydraulic cylinder assembly 11′. Firstand second accumulators 63, 64 are connected to the first and secondanti-sway fluid lines 61, 62 to prevent excessive pressure spikes in thesystem during operation.

The first and second accumulators 63, 64 can have adjustable pressuresettings to provide a range of anti-sway control. The expansioncapacities of the accumulators 63, 64 can be substantially smaller thanthe expansion capacities of the external spring packs 59, 60 because thesway-control system only requires a relatively small volume of hydraulicfluid for sway control compared to the larger volume of fluid thatpasses from the hydraulic cylinder assemblies 11′, 12′ into the externalspring packs 59, 60 when the vehicle travels over uneven terrain, etc.

The hydraulic reservoir 42 for the vehicle suspension system 10, 50 canbe located in the spare tire compartment of the vehicle. For example, ina pickup truck, the spare tire compartment 65 is located under thepickup truck bed 66. As illustrated in FIG. 13, the hydraulic reservoir42 is arranged in the spare tire compartment 65 and arranged to benested in the wheel cavity of the spare tire 67. In the case of a pickuptruck, the hydraulic reservoir 42 is mounted in the spare tirecompartment 65 under the pickup truck bed 66 with a hanging bracket forthe spare tire 67 hanging down from a center of the hydraulic reservoir42. The spare tire 67 can then be hung in the spare tire compartment 65with the hydraulic reservoir 42 nested in the wheel cavity above thespare tire to optimize space.

While the invention has been specifically described in connection withspecific embodiments thereof, it is to be understood that this is by wayof illustration and not of limitation, and the scope of the appendedclaims should be construed as broadly as the prior art will permit.

What is claimed is:
 1. A vehicle suspension system, comprising: atelescoping multi-stage hydraulic cylinder assembly arranged toselectively lift a vehicle body relative to a vehicle wheel whenextended and lower the vehicle body relative to the vehicle wheel whencontracted; an external spring pack in fluid connection with thehydraulic cylinder assembly to maintain a spring force on the suspensionsystem over a range of telescopic movement of said hydraulic cylinderassembly; and a fluid damping valve for damping telescopic movement ofthe hydraulic cylinder assembly by restricting fluid flow between thehydraulic cylinder assembly and the spring pack; wherein said hydrauliccylinder assembly comprises a base cylinder, at least one intermediatecylinder arranged for sliding telescopic movement within said basecylinder, and a shaft arranged for sliding telescopic movement withinsaid at least one intermediate cylinder, wherein said base cylinder,said at least one intermediate cylinder and said shaft are nested withinand movable relative to each other to provide at least two stages oftelescopic movement for said hydraulic cylinder assembly, said basecylinder and said at least one intermediate cylinder together define asingle internal chamber in fluid connection with said external springpack, and a length of said hydraulic cylinder assembly in a fullyextended condition is more than a length of said hydraulic cylinderassembly in a fully contracted condition.
 2. The vehicle suspensionsystem according to claim 1, wherein said spring pack is located remotefrom said hydraulic cylinder assembly.
 3. The vehicle suspension systemaccording to claim 1, wherein said spring pack comprises a cylindricalchamber in fluid connection with said hydraulic cylinder assembly, apiston arranged for sliding movement within said cylindrical chamber,and a spring arranged to bias said piston in a direction that applieshydraulic pressure to said hydraulic cylinder assembly.
 4. The vehiclesuspension system according to claim 3, wherein said spring comprises acoil spring arranged within said spring pack.
 5. The vehicle suspensionsystem according to claim 3, wherein said spring comprises a gas underpressure located within a chamber separated by said piston from saidcylindrical chamber in fluid connection with said hydraulic cylinderassembly.
 6. The vehicle suspension system according to claim 3, whereinsaid spring comprises a coil spring arranged within said spring pack anda gas under pressure within a chamber separated by said piston from saidcylindrical chamber in fluid connection with said hydraulic cylinderassembly.
 7. The vehicle suspension system according to claim 1, furthercomprising a suspension position sensor arranged to measure a positionof the vehicle body relative to the vehicle wheel to provide feedbackfor adjusting a height of the vehicle body.
 8. The vehicle suspensionsystem according to claim 1, further comprising a control valve having apressure inlet connected to a source of fluid pressure, a pressurereturn connected to a hydraulic reservoir, a port connected to saidhydraulic cylinder assembly, and a controller for moving the valvebetween a first position in which hydraulic fluid flows from thepressure inlet to said hydraulic cylinder assembly, a second position inwhich hydraulic fluid flows through from said hydraulic cylinderassembly to said hydraulic reservoir, and a third position in whichhydraulic fluid is blocked from flowing through said control valve. 9.The vehicle suspension system according to claim 1, wherein said fluiddamping valve comprises an inline valve system that dampens fluid forcesas hydraulic fluid passes in either direction between the hydrauliccylinder assembly and the spring pack.
 10. The vehicle suspension systemaccording to claim 1, wherein said external spring pack maintains asubstantially constant spring force on the suspension system over arange of telescopic movement of said hydraulic cylinder assembly toaccommodate height changes of the vehicle body relative to the vehiclewheel while maintaining a comfortable ride.
 11. A vehicle comprising: avehicle body; a plurality of wheels; and a suspension system thatconnects the vehicle body to said plurality of wheels and allowsrelative motion between said vehicle body and said wheels, saidsuspension system comprising: a plurality of telescoping multi-stagehydraulic cylinder assemblies arranged to selectively lift the vehiclebody relative to the wheels when extended and to lower the vehicle bodyrelative to the wheels when contracted; a plurality of external springpacks in fluid connection with the plurality of hydraulic cylinderassemblies to maintain spring forces on the suspension system over arange of telescopic movement of said hydraulic cylinder assemblies; anda plurality of fluid damping valves for damping telescopic movement ofthe hydraulic cylinder assemblies by restricting fluid flow between thehydraulic cylinder assemblies and the spring packs; wherein each of saidhydraulic cylinder assemblies comprises a base cylinder, at least oneintermediate cylinder arranged for sliding telescopic movement withinsaid base cylinder, and a shaft arranged for sliding telescopic movementwithin said at least one intermediate cylinder, wherein said basecylinder, said at least one intermediate cylinder and said shaft arenested within and movable relative to each other to provide at least twostages of telescopic movement for said hydraulic cylinder assembly,wherein said base cylinder and said at least one intermediate cylindertogether define a single internal chamber within each hydraulic cylinderassembly in fluid connection with a respective one of said externalspring packs, and wherein a length of each of said hydraulic cylinderassemblies in a fully extended condition is more than a length thereofin a fully contracted condition.
 12. The vehicle according to claim 11,wherein said plurality of wheels comprises four wheels, said pluralityof hydraulic cylinder assemblies comprises four hydraulic cylinderassemblies associated with said four wheels, respectively, saidplurality of external spring packs comprises four external spring packsassociated with said four hydraulic cylinder assemblies, respectively,and said plurality of fluid damping valves comprises four fluid dampingvalves associated with said four hydraulic cylinder assemblies and saidfour external spring packs, respectively.
 13. The vehicle according toclaim 11, wherein said spring packs are located remote from saidhydraulic cylinder assemblies and each comprises a cylindrical chamberin fluid connection with a respective one of said hydraulic cylinderassemblies, a piston arranged for sliding movement within saidcylindrical chamber, and a spring arranged to bias said piston in adirection that applies hydraulic pressure to the respective hydrauliccylinder assembly.
 14. The vehicle according to claim 11, furthercomprising a plurality of suspension position sensors associated withsaid hydraulic cylinder assemblies, said suspension sensors each beingarranged to measure positions of the vehicle body relative to arespective one of the wheels to provide feedback for adjusting a heightand levelness of the vehicle body.
 15. The vehicle according to claim11, further comprising a control valve assembly for controllinghydraulic fluid flow into and out of said hydraulic cylinder assemblies,said control valve assembly having a pressure inlet connected to asource of fluid pressure, a pressure return connected to a hydraulicreservoir, and a plurality of valve members that individually control aflow of hydraulic fluid from said source of fluid pressure to each ofsaid hydraulic cylinder assemblies, and a flow of hydraulic fluid fromeach of said hydraulic cylinder assemblies to said reservoir.
 16. Thevehicle according to claim 11, wherein said external spring packsmaintain a substantially constant spring force on the suspension systemover a range of telescopic movement of said hydraulic cylinderassemblies to accommodate height changes of the vehicle body relative tothe wheels while maintaining a comfortable ride.
 17. A vehiclesuspension comprising: first and second telescoping multi-stagehydraulic cylinder assemblies mounted on right and left sides of avehicle, respectively, said hydraulic cylinder assemblies being arrangedto selectively lift the vehicle when extended and lower the vehicle whencontracted, wherein each of said hydraulic cylinder assemblies comprisesa base cylinder, an intermediate cylinder arranged for slidingtelescopic movement within said base cylinder, and a shaft arranged forsliding telescopic movement within said at least one intermediatecylinder, wherein said base cylinder, said at least one intermediatecylinder and said shaft are nested within each other to provide at leasttwo stages of telescopic movement for said hydraulic cylinder assembly,wherein said base cylinder and said at least one intermediate cylindertogether define a single internal chamber within each hydraulic cylinderassembly, wherein a length of each of said hydraulic cylinder assembliesin a fully extended condition is more than a length thereof in a fullycontracted condition, and wherein each of said hydraulic cylinderassemblies are two-way cylinder assemblies having a pressure side and areservoir side; first and second external spring packs in fluidconnection with the internal chambers of said first and second hydrauliccylinder assemblies, respectively, to maintain spring forces on thehydraulic cylinder assemblies over a range of telescopic movement ofsaid hydraulic cylinder assemblies; fluid damping valves for dampingmovement of the hydraulic cylinder assemblies by restricting fluid flowbetween the hydraulic cylinder assemblies and the spring packs; and ananti-sway system comprising a first anti-sway fluid line connectedbetween a primary side of the first hydraulic cylinder assembly and asecondary side of the second hydraulic cylinder assembly, and a secondanti-sway fluid line connected between a primary side of the secondhydraulic cylinder assembly and a secondary side of the first hydrauliccylinder assembly.